Staff: Mentor

For block B, the force in the the rope to point A is sin∅/200lb. For block C, the force in the rope to point a is sin(30)/100 =50lb .

Is this correct so far?

No. First things first. What's the tension in the rope connecting to B and the rope connecting to C? Hint: No calculation is required. (Consider the forces on B and C.) Then you can worry about the force components acting on point A.

Careful how you write things: don't confuse sin(30)/100 with 100*sin(30).